This section provides background information related to the present disclosure which is not necessarily prior art.
Electric machines typically are devices that convert electrical energy into mechanical energy (motors) or devices that convert mechanical energy into electrical energy (generators, alternators). These electric machines utilize electrical brushes, typically a mix of copper and carbon, to transfer electricity between a pigtail wire and a rotating commutator mounted on an armature or a rotor mounted in the electric machine.
The electrical brushes are typically held in contact with the commutator using mechanical springs. As the electrical brushes wear beyond the point of a minimum brush spring force, the mechanical springs may no longer maintain the contact between the electrical brush and the commutator.
For automotive vehicles, one of the most common problems for starter motors and alternators is the wearing out of the electrical brushes. Existing starter motors and alternators provide no warning to the operator of the vehicle when the electrical brushes approach the point of wearing out. Even though electrical brush wear out does not typically occur until after many years of vehicle service, the fact remains that no warning is given and the resulting inoperative condition of the starter motor or the alternator can cause significant inconvenience. On the day when the electrical brushes wear out, the resulting inoperative condition of the starter motor or the alternator can leave the vehicle operator stranded when he attempts to start a stopped vehicle or it can leave the vehicle operator stranded after an hour or so while the vehicle runs on its battery charge.
As automotive vehicles are developed into electric automobiles and hybrid automobiles for example, starter motors and alternators will be cycled more frequently creating a much more severe operating environment. This has the potential to increase the duty cycle of the electrical brushes and to place more emphasis on the life of the electrical brushes and some type of warning being given when the wear of the electrical brushes is near its maximum wear condition.